Current breaker circuit for storage devices, and abnormality detection circuit

ABSTRACT

A current breaker circuit by which currents flowing in loads respectively connected to a plurality of storage devices connected in series are broken in accordance with a single external control signal. The current breaker circuit includes semiconductor switching devices inserted between the storage devices and the loads respectively, a unit for supplying the external control signal to at least one of the semiconductor switching devices, and control signal generating units for generating ON/OFF signals in accordance with turning ON/OFF of the semiconductor switching device supplied with the external control signal so as to supply the ON/OFF signals to the other semiconductor switching devices.

BACKGROUND OF THE INVENTION

The present invention relates to a current breaker circuit for cutting off a plurality of storage devices connected in series, and load circuits (voltage detection circuit) for the respective storage devices in accordance with a single external signal so that a leakage current can be prevented; to a voltage detection circuit for such storage devices; and an abnormality detection circuit.

In a circuit in which a plurality of storage devices are connected in series and loads are connected to the storage devices respectively, it has been heretofore necessary to prevent consumption of energy accumulated in the storage devices.

To this end, there have been related-art current breaker circuits as shown in FIGS. 6 and 7. Such current breaker circuits can disconnect all the loads in accordance with a single control signal when the storage devices and the loads are disconnected respectively.

The configurations and operations of the related-art circuits will be described below with reference to FIGS. 6 and 7.

FIG. 6 shows an example of a related-art current breaker circuit.

In FIG. 6, storage devices B1 to B4 are connected in series. In addition, loads R1 to R4 are connected to the storage devices B1 to B4 respectively.

In addition, semiconductor switching devices Q1 to Q4 are connected between the storage devices B1 to B4 and the loads R1 to R4 respectively.

The bases of the semiconductor switching devices Q1 to Q4 which are control terminals are connected in common through diodes d1 to d4 and resistors r1 to r4 so that an external signal switch S provided between the common connection terminal and the negative terminal of the storage device B1 can be turned ON or OFF in accordance with an ON/OFF signal.

As for the operation of this current breaker circuit, when the external signal switch S provided between the common connection terminal of the resistors r1 to r4 and the negative terminal of the storage device B1 is turned ON in accordance with the ON/OFF signal supplied to the switch S, all the semiconductor switching devices Q1 to Q4 are turned ON. Thus, currents are supplied from the storage devices B1 to B4 to the loads R1 to R4 corresponding and respectively.

On the contrary, when the external signal switch S is turned OFF, the semiconductor switching devices Q1 to Q4 are turned OFF so that no current is supplied to the loads R1 to R4.

In this current breaker circuit, all the semiconductor switching devices Q1 to Q4 can be turned ON/OFF in accordance with a single ON/OFF signal. However, on the higher potential side (the storage device B4 side in FIG. 6) of the storage devices connected in series, the voltage between the emitter of the semiconductor switching device and the negative terminal of the storage device B1 increases. Thus, there is a problem that the power loss of the resistor increases and a high voltage switch has to be used as the external signal switch S.

FIG. 7 shows another example of a related-art current breaker circuit.

In FIG. 7, storage devices B1 to B4 are connected in series in the same manner as those in FIG. 6.

In addition, loads R1 to R4 are connected to the storage devices B1 to B4 respectively.

In addition, photo-couplers (photo-relays) PH1 to PH4 are connected between the storage devices B1 to B4 and the loads R1 to R4 respectively.

All of light-emitting diodes of the photo-couplers PH1 to PH4 are connected in series, and designed so that a current is supplied between opposite terminals of each light-emitting diode in accordance with an ON/OFF signal given to the switch S.

As for the operation of this current breaker circuit, all the photo-couplers PH1 to PH4 are turned ON when a current is supplied to the light-emitting diodes connected in series. Thus, currents are supplied from the storage devices B1 to B4 to the loads R1 to R4 respectively.

On the contrary, when no current is supplied to the light-emitting diodes connected in series, all the photo-couplers PH1 to PH4 are turned OFF. Thus, no current is supplied to the loads R1 to R4.

In this current breaker circuit, all the semiconductor switching devices Q1 to Q4 can be turned ON/OFF in accordance with a single ON/OFF signal. Accordingly, the problem of withstanding voltage as in the circuit of FIG. 6 is solved. On the other hand, there is however a problem that a large number of expensive photo-couplers or the like have to be used.

SUMMARY OF THE INVENTION

In order to solve the defects in the related-art current breaker circuits, an object of the invention is to provide a current breaker circuit which can surely break currents supplied to a plurality of loads from a plurality of storage devices connected in series, in accordance with a single external control signal without using any high-voltage withstanding switch or any expensive photo-coupler; and to provide a voltage detection circuit for such storage devices.

In addition, another object of the invention is to provide an abnormality detection circuit for such a current breaker circuit.

To solve the foregoing problems, according to the invention, there is provided a current breaker circuit for turning off currents flowing in loads in accordance with a single external control signal, while the loads are connected between terminals of a plurality of storage devices connected in series respectively. The current breaker circuit includes semiconductor switching devices inserted between the storage devices and the loads respectively, a unit for supplying the external control signal to at least one of the semiconductor switching devices, and a control signal generating unit for generating an ON/OFF signal in response to an electric change based on turning ON/OFF of the semiconductor switching device supplied with the external control signal, the ON/OFF signal being supplied to other semiconductor switching devices.

Accordingly, currents supplied from the plurality of storage devices connected in series to the plurality of loads can be surely broken in accordance with a single external control signal without using any high-voltage withstanding switch or any expensive photo-coupler.

The loads in this configuration may be formed as pieces of a voltage detection circuit for storage devices. In this case, the current breaker circuit for storage devices has features in that:

(1) a plurality of storage devices are connected in series;

(2) a piece of the voltage detection circuit is connected for every unit cell of the plurality of storage devices;

(3) each piece of the voltage detection circuit is connected between a positive terminal and a negative terminal of a corresponding unit cell of the plurality of storage devices;

(4) a semiconductor switching device is inserted between the storage device and the voltage detection circuit;

(5) a control signal generator circuit for supplying a control signal to a control electrode of the semiconductor switching device inserted in series is connected to the control electrode of the semiconductor switching device; and

(6) the control signal generator circuit detects a voltage change on the voltage detection circuit side of the semiconductor switching devices connected to the storage devices other than the storage device to which the semiconductor switching device for supplying the control signal is connected, and the control signal generator circuit generates the control signal in accordance with the detection of the voltage change.

In addition, when the external control signal is supplied to at least two adjacent ones of the semiconductor switching devices simultaneously, the current breaker circuit for storage devices can be formed out of a smaller number of constituent members.

In addition, when the control signal generating unit supplies the ON/OFF signal to at least two adjacent ones of the semiconductor switching devices simultaneously, the number of the control signal generator circuits can be reduced.

In addition, when the semiconductor switching device supplied with the external control signal is formed as a semiconductor switching device connected to a lower voltage side among the storage devices connected in series, the potential of the switch can be made lower.

In addition, when the ON/OFF signal is supplied to the semiconductor switching devices through diodes respectively, high voltage can be prevented from being applied to the control terminals of the semiconductor switching devices.

In addition, when the loads are formed as a voltage detection circuit for detecting terminal-to-terminal voltages of the plurality of storage devices connected in series, even a very small current flowing in the voltage detection circuit can be broken surely.

Further, a voltage detection circuit for storage devices according to the invention has features in that:

a plurality of terminal-to-terminal voltage generator circuits are provided;

each of the terminal-to-terminal voltage generator circuits is constituted by a storage device, a subtractor circuit and an A/D converter circuit, the subtractor circuit being supplied with a positive terminal voltage (Vn+1) and a negative terminal voltage (Vn) of the storage device and outputting a terminal-to-terminal voltage (Vno) of the storage device, the A/D converter circuit being supplied with the output of the subtractor circuit and outputting digital data;

the storage devices provided in the plurality of terminal-to-terminal voltage generator circuits are connected in series;

outputs of the A/D converter circuits provided in the plurality of terminal-to-terminal voltage generator circuits are supplied to a selector circuit, which selects one piece of output data from the parallel output data supplied from the plurality of A/D converter circuits; and

the selected piece of output data is supplied to a parallel-to-serial converter circuit, which converts the piece of output data into serial data, and outputs the converted serial data, so that a terminal-to-terminal voltage of any desired one of the plurality of storage devices connected in series is obtained as the serial data.

In the voltage detection circuit for storage devices configured thus, the terminal-to-terminal voltages of the plurality of storage devices connected in series can be detected accurately and selectively respectively to be outputted.

In addition, an external select control signal may be supplied to the selector circuit.

In addition, a plurality of parallel-to-serial converter circuits may be provided at a pre-stage of the selector circuit so that the selector circuit can select one from the outputs converted into serial data by the parallel-to-serial converter circuits.

In addition, when the serial data and/or the select control signal are supplied through an isolator, the serial data and/or the select control signal can be electrically isolated from external circuits.

Further, a voltage detection circuit for storage devices according to the invention has features in that:

at least a plurality of terminal-to-terminal voltage generator circuits are provided;

each of the terminal-to-terminal voltage generator circuits is constituted by a storage device, a subtractor circuit and an A/D converter circuit, the subtractor circuit being supplied with a positive terminal voltage (Vn+1) and a negative terminal voltage (Vn) of the storage device and outputting a terminal-to-terminal voltage (Vno) of the storage device, the A/D converter circuit being supplied with the output of the subtractor circuit and outputting digital data;

the storage devices provided in the plurality of terminal-to-terminal voltage generator circuits are connected in series;

a selector circuit selects one piece of output data from output data of the A/D converter circuits respectively provided in the plurality of terminal-to-terminal voltage generator circuits; and

the selected piece of output data is supplied to a parallel-to-serial converter circuit, which converts the supplied piece of output data into serial data;

the terminal-to-terminal voltage generator circuits, the selector circuit and the parallel-to-serial converter circuit are included in a single module; and

a pair of opposite terminals of the plurality of storage devices connected in series, and an output terminal of the serial data are led out as external terminals of the module.

When the single module is configured thus, a desired system can be constructed easily by use of a plurality of such modules.

In addition, when a select control signal from the outside of the module is supplied as a serial signal to the selector circuit, signals can be transmitted/received between the module and the outside through a small number of signal lines.

In addition, a plurality of parallel-to-serial converter circuits may be provided at a pre-stage of the selector circuit so that the selector circuit can select one from the outputs converted into serial data by the parallel-to-serial converter circuits.

In addition, an isolator for electrically isolating the serial data and/or the select control signal may be provided in the module.

Further, according to the invention, an abnormality detection circuit for detecting abnormality of a current breaker circuit breaking currents in accordance with a single external control signal is provided. The currents flow into a plurality of loads which are respectively connected between terminals of a plurality of storage devices connected in series. When operation abnormality of the current breaker circuit is detected on the basis of the single external control signal and a terminal-to-terminal voltage of a final-stage one of the loads in the abnormality detection circuit, abnormality of the operation of the current breaker circuit as a whole can be detected easily.

In addition, a first photo-coupler and a second photo-coupler may be provided and connected in series to opposite terminals of the final-stage load respectively. In this case, the external control signal is supplied to the second photo-coupler only for an abnormality detection period so as to turn on the abnormality detection circuit and thereby obtain a detection result through the first photo-coupler. Thus, a current is allowed to flow into a light emitting device of the first photo-coupler and a light receiving device of the second photo-coupler only for the detection period. Accordingly, it is not necessary to make a constant conduction. It is therefore possible to prevent useless consumption of electric power.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing the configuration of a first current breaker circuit according to the invention.

FIG. 2 is a diagram showing the configuration of a second current breaker circuit according to the invention.

FIG. 3 is a diagram showing an abnormality detection circuit for a current breaker circuit according to the invention.

FIG. 4 is a diagram showing the details of a voltage detection circuit according to the invention.

FIG. 5 is a diagram showing the details of another voltage detection circuit according to the invention.

FIG. 6 is a diagram showing the configuration of a related-art current breaker circuit.

FIG. 7 is a diagram showing the configuration of another related-art current breaker circuit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a current breaker circuit according to a first embodiment of the invention.

In FIG. 1, storage devices B1 to B4 are connected in series.

In addition, loads R1 to R4 are connected to the storage devices B1 to B4 respectively.

In addition, semiconductor switching devices Q1 to Q4 are connected between the storage devices B1 to B4 and the loads R1 to R4 respectively.

The base of the semiconductor switching device (e.g. transistor or FET) Q1 which is a control terminal is connected to one end of a switch S through a resistor r1. The switch S is turned ON/OFF in accordance with an external control signal.

Further, the base of the semiconductor switching device Q2 which is a control terminal is connected to the collector of a transistor q1 through a resistor r2. The transistor q1 constitutes a control signal generator circuit.

The base of the transistor q1 is connected to the collector of the semiconductor switching device Q1 through a resistor r11, while the emitter of the transistor q1 is connected to the negative terminal of the load R1.

In addition, the base of the semiconductor switching device Q3 which is a control terminal is connected to the collector of a transistor q2 through a resistor r3. The transistor q2 constitutes a control signal generator circuit.

The base of the transistor q2 is connected to the collector of the semiconductor switching device Q2 through a resistor r22, while the emitter of the transistor q2 is connected to the negative terminal of the load R2.

In addition, the base of the semiconductor switching device Q4 which is a control terminal is connected to the collector of a transistor q3 through a resistor r4. The transistor q3 constitutes a control signal generator circuit.

The base of the transistor q3 is connected to the collector of the semiconductor switching device Q3 through a resistor r33, while the emitter of the transistor q3 is connected to the negative terminal of the load R3.

The current breaker circuit shown in FIG. 1 operates as follows.

First, when the switch S is turned ON in accordance with an external control signal, a current flows from the emitter to the base in the semiconductor switching device Q1. Thus, the semiconductor switching device Q1 is turned ON.

When the semiconductor switching device Q1 is turned ON, a current from the collector of the semiconductor switching device Q1 flows from the base to the emitter in the transistor q1 which constitutes a control signal generator circuit. Thus, the transistor q1 is turned ON.

Then, when the transistor q1 is turned ON, a current flows from the emitter to the base in the semiconductor switching device Q2. Thus, the semiconductor switching device Q2 is turned ON.

Further, when the semiconductor switching device Q2 is turned ON, a current from the collector of the semiconductor switching device Q2 flows from the base to the emitter in the transistor q2 which constitutes a control signal generator circuit. Thus, the transistor q2 is turned ON.

Then, when the transistor q2 is turned ON, a current flows from the emitter to the base in the semiconductor switching device Q3. Thus, the semiconductor switching device Q3 is turned ON.

Further, when the semiconductor switching device Q3 is turned ON, a current from the collector of the semiconductor switching device Q3 flows from the base to the emitter in the transistor q3 which constitutes a control signal generator circuit. Thus, the transistor q3 is turned ON.

Then, when the transistor q3 is turned ON, a current flows from the emitter to the base in the semiconductor switching device Q4. Thus, the semiconductor switching device Q4 is turned ON.

In such a manner, when the switch S is turned ON in accordance with an external control signal, all the semiconductor switching devices Q1 to Q4 are turned ON.

On the contrary, when the switch S is turned OFF in accordance with an external control signal, no current flows from the emitter to the base in the semiconductor switching device Q1. Thus, the semiconductor switching device Q1 is turned OFF.

When the semiconductor switching device Q1 is turned OFF, the transistors q1 to q3 which constitute control signal generator circuits respectively are not allowed to be turned ON, so that all the semiconductor switching devices Q1 to Q4 are turned OFF.

In such a manner, in the current breaker circuit shown in FIG. 1 according to the first embodiment, all the semiconductor switching devices Q1 to Q4 are allowed to be turned ON/OFF in accordance with a single external control single (ON/OFF signal). Thus, the current breaker circuit can be constructed without using any high-voltage withstanding switch, any expensive photo-coupler, or the like.

FIG. 2 is a diagram showing a current breaker circuit according to a second embodiment of the invention.

In FIG. 2, storage devices B1 to B4 are connected in series.

In addition, loads R1 to R4 are connected to the storage devices B1 to B4 respectively.

In addition, semiconductor switching devices Q1 to Q4 are connected between the storage devices B1 to B4 and the loads R1 to R4 respectively.

The bases of the semiconductor switching devices Q1 and Q2 which are control terminals are connected to one end of a switch S through series circuits of resistors r1 and r2 and diodes d1 and d2 respectively. The switch S is turned ON/OFF in accordance with an external control signal.

In addition, the bases of the semiconductor switching devices Q3 and Q4 which are control terminals are connected to the collector of a transistor q1 through series circuits of resistors r3 and r4 and diodes d3 and d4 respectively. The transistor q1 constitutes control signal generator circuits.

The base of the transistor q1 is connected to the collector of the semiconductor switching device Q2 through a resistor r11, while the emitter of the transistor q1 is connected to the negative terminal of the load R2.

The current breaker circuit shown in FIG. 2 operates as follows.

First, when the switch S is turned ON in accordance with an external control signal, a current flows from the emitter to the base in each of the semiconductor switching devices Q1 and Q2. Thus, both the semiconductor switching devices Q1 and Q2 are turned ON.

When the semiconductor switching devices Q1 and Q2 are turned ON, a current from the collector of the semiconductor switching device Q2 flows from the base to the emitter in the transistor q1 which constitutes the control signal generator circuit. Thus, the transistor q1 is turned ON.

Then, when the transistor q1 is turned ON, a current flows from the emitter to the base in each of the semiconductor switching devices Q3 and Q4. Thus, the semiconductor switching devices Q3 and Q4 are turned ON.

In such a manner, when the switch S is turned ON in accordance with an external control signal, all the semiconductor switching devices Q1 to Q4 are turned ON.

On the contrary, when the switch S is turned OFF in accordance with an external control signal, the semiconductor switching devices Q1 and Q2 are turned OFF because no current flows from the emitter to the base of each of the semiconductor switching devices Q1 and Q2.

When the semiconductor switching device Q2 is turned OFF, the transistor q1 constituting the respective control signal generator circuits cannot be turned ON. Thus, all the semiconductor switching devices Q1 to Q4 are turned OFF.

In such a manner, in the current breaker circuit according to the first embodiment as shown in FIG. 2, all the semiconductor switching devices Q1 to Q4 can be turned ON/OFF in accordance with a single external control signal (ON/OFF signal). In addition, the current breaker circuit can be constructed without using any high-voltage withstanding switch or any expensive photo-coupler or the like. At the same time, since two semiconductor switching devices are turned ON/OFF in common, the number of control signal generator circuits can be reduced.

Incidentally, although two semiconductor switching devices are turned ON/OFF in common in FIG. 2, two or more semiconductor switching devices may be turned ON/OFF in common in accordance with the withstanding voltages of the respective devices.

Although the current breaker circuits in FIGS. 1 and 2 are described on the assumption that currents from a plurality of storage devices connected in series are supplied to loads through a plurality of semiconductor switching devices, higher effect can be obtained if the loads provided in this case are formed as a voltage detection circuit for detecting individual terminal-to-terminal voltages of the storage devices.

In a system using a plurality of storage devices connected in series, even when the system is down, currents flow, though slightly, into the voltage detection circuit (corresponding to the loads in FIGS. 1 and 2) for detecting terminal-to-terminal voltages of the plurality of storage devices connected in series.

When such a state continues for a long time, currents are released from the storage devices. Therefore, when the system is down, it is necessary to break currents flowing into the voltage detection circuit.

In such a case, the current breaker circuits shown in FIGS. 1 and 2 are effective in preventing the storage devices from discharging when an external control signal is generated in response to the system down.

Further, the current breaker circuit shown in FIG. 1 or 2 may be formed into a module as a unit block. In this case, lower-voltage-side and higher-voltage side terminals of the plurality of storage devices connected in series, control terminals for the semiconductor switching devices, and an output terminal corresponding to the electric continuity of the semiconductor switching devices are provided outside the unit module. When a plurality of such modules are connected in cascade, a system adapted to any desired voltage can be constructed.

Also in this case, a plurality of semiconductor switching devices lying over the plurality of modules in the system can be turned ON/OFF in accordance with a single external signal.

FIG. 3 is a diagram showing an abnormality detection circuit for a current breaker circuit according to a third embodiment of the invention.

In FIG. 3, storage devices B1 to B4 are connected in series.

In addition, loads R1 to R4 are connected to the storage devices B1 to B4 respectively.

In addition, semiconductor switching devices Q1 to Q4 are connected between the storage devices B1 to B4 and the loads R1 to R4 respectively.

The base of the semiconductor switching device (e.g. transistor or FET) Q1 which is a control terminal is connected to be supplied with the output of a photo-coupler PH3 which is turned ON/OFF in accordance with an external control signal c.

Further, the base of the semiconductor switching device Q2 which is a control terminal is connected to the collector of a transistor q1 through a resistor. The transistor q1 constitutes a control signal generator circuit.

The base of the transistor q1 is voltage-divided by resistors and connected to the opposite ends of the load R1.

In addition, the base of the semiconductor switching device Q3 which is a control terminal is connected to the collector of a transistor q2 through a resistor. The transistor q2 constitutes a control signal generator circuit.

The base of the transistor q2 is voltage-divided by resistors and connected to the opposite ends of the load R2.

In addition, the base of the semiconductor switching device Q4 which is a control terminal is connected to the collector of a transistor q3 through a resistor. The transistor q3 constitutes a control signal generator circuit.

The base of the transistor q3 is voltage-divided by resistors and connected to the opposite ends of the load R3.

In addition, a transistor q4 constitutes a control signal generator circuit. The collector of the transistor q4 is led out to be connected to a next-stage semiconductor switching device.

The base of the transistor q4 is voltage-divided by resistors and connected to the opposite ends of the load R4.

Further, a light emitting device of a photo-coupler PH1 and a light receiving device of a photo-coupler PH2 are connected in series to the opposite ends of the final-stage load R4 through a resistor.

A signal b is supplied to the light receiving device of the photo-coupler PH2 while an output signal a is extracted from the light receiving device of the photo-coupler PH1.

Next, the operation of the abnormality detection circuit for the current breaker circuit will be described.

In accordance with whether there is a signal c supplied to a light emitting device of a photo-coupler PH3 or not, the light emitting device is turned ON/OFF so that the semiconductor switching devices Q1 to Q4 are turned ON/OFF sequentially in the same manner as in FIG. 1.

The signal b is designed to be supplied to the photo-coupler PH2 only for a period for detecting whether there is a signal a from the photo-coupler PH1 or not. Thus, the useless consumption of electric power is prevented.

If the signal a is obtained (if the light receiving device of the photo-coupler PH1 is turned ON) at the time when the signal c is present (at the time when a current is made to flow into the light emitting device of the photo-coupler PH3), this abnormality detection circuit can conclude that the current breaker circuit operates normally.

Further, if the signal a is obtained (if the light receiving device of the photo-coupler PH1 is turned OFF) at the time when the signal c is present (at the time when a current is made to flow into the light emitting device of the photo-coupler PH3), the abnormality detection circuit can conclude that the current breaker circuit is abnormal.

Further, if the signal a is obtained (if the light receiving device of the photo-coupler PH1 is turned ON) at the time when the signal c is absent (at the time when no current is made to flow into the light emitting device of the photo-coupler PH3), the abnormality detection circuit can conclude that the current breaker circuit is abnormal.

Further, if the signal a is obtained (if the light receiving device of the photo-coupler PH1 is turned OFF) at the time when the signal c is absent (at the time when no current is made to flow into the light emitting device of the photo-coupler PH3), the abnormality detection circuit can conclude that the current breaker circuit operates normally.

On the basis of the results of these four cases, the abnormality detection circuit can judge whether the current breaker circuit is normal or abnormal.

Next, with reference to FIG. 4, description will be made on the details of a voltage detection circuit which is an example of loads on the current breaker circuit.

In a module in which a plurality of storage devices have been connected thus in series, the terminal-to-terminal voltages of the storage devices change individually. Therefore, a voltage detection circuit for detecting an accurate terminal-to-terminal voltage of each storage device is required.

FIG. 4 is a voltage detection circuit for detecting individual terminal-to-terminal voltages of a plurality of storage devices of a storage device group in which the storage devices have been connected in series.

In FIG. 4, the reference signs B1 to B4 represent storage devices connected in series. Terminal-to-terminal voltage generator circuits VP1 to VP4 are connected between positive terminals and negative terminals of the storage devices respectively. An output is selected from the outputs of the terminal-to-terminal voltage generator circuits by a selector circuit SE which is, for example, constituted by a multi-switchable IC and so on. The selected output is supplied through a parallel-to-serial converter circuit P/S.

In addition, the terminal-to-terminal voltage generator circuits VP2 to VP4 are constituted by subtractor circuits D2 to D4 and analog-to-digital converter circuits A/D2 to A/D4, which are constituted by operational amplifiers and so on, respectively.

Incidentally, in the terminal-to-terminal voltage generator circuit VP1 to be connected to a lower-voltage-side storage device, the positive terminal voltage of the storage device B1 is connected to an analog-to-digital converter circuit A/D1 without passing through any subtractor circuit.

Incidentally, also when the terminal-to-terminal voltage generator circuit VP1 to be connected to a lower-voltage-side storage device is connected to the analog-to-digital converter circuit A/D1 through a subtractor circuit, similar operation can be carried out.

In each of the subtractor circuits D2 to D4, the negative terminal voltage of the storage device to which the subtractor circuit is connected is subtracted from the positive terminal voltage thereof so that the terminal-to-terminal voltage of the storage device is detected.

The detected terminal-to-terminal voltages of the storage devices B1 to B4 are supplied to the selector circuit SE through their corresponding analog-to-digital converter circuits A/D1 to A/D4 respectively. The detected voltage of a storage device selected by the selector circuit SE is outputted as serial data through the parallel-to-serial converter circuit P/S.

Incidentally, though not shown in FIG. 4, it is effective that the output of the parallel-to-serial converter circuit P/S is supplied through an isolator such as a photo-coupler. In this case, the output can be electrically isolated from the storage devices.

In addition, the detected voltages of the plurality of storage devices B1 to B4 may be outputted selectively in a predetermined order in the selector circuit by a CPU or the like. Alternatively, a detected voltage of a desired storage device may be outputted in accordance with a not-shown external select control signal.

In addition, the contents of data to be outputted as serial data may include not only the terminal-to-terminal voltage of the detected storage device but also overvoltage or undervoltage information of the respective storage devices.

In addition, although description in FIG. 4 has be made on the case where the detected voltage selected by the selector circuit is converted into a serial signal by the parallel-to-serial converter circuit, a plurality of parallel-to-serial converter circuits may be provided so that detected voltages are converted into serial signals before one is selected from the serial signals by the selector circuit.

FIG. 5 shows another example of a voltage detection circuit for detecting individual terminal-to-terminal voltages of a plurality of storage devices of a storage device group in which the storage devices have been connected in series.

In FIG. 5, the reference signs B1 to B4 represent storage devices connected in series. Terminal-to-terminal voltage generator circuits VP1 to VP4 are connected between positive terminals and negative terminals of the storage devices respectively. An output is selected from the outputs of the terminal-to-terminal voltage generator circuits by a selector circuit SE. The selected output is supplied through a parallel-to-serial converter circuit P/S. (In FIG. 5, the parallel-to-serial converter circuit P/S to be supplied with the output of the selector circuit SE is not shown).

In addition, the terminal-to-terminal voltage generator circuits VP2 to VP4 are constituted by subtractor circuits D2 to D4 and analog-to-digital converter circuits A/D2 to A/D4, which are constituted by operational amplifiers and so on, respectively.

Incidentally, in the terminal-to-terminal voltage generator circuit VP1 to be connected to a lower-voltage-side storage device, the positive terminal voltage of the storage device B1 is connected to an analog-to-digital converter circuit A/D1 without passing through any subtractor circuit.

Incidentally, also when the terminal-to-terminal voltage generator circuit VP1 to be connected to a lower-voltage-side storage device is connected to the analog-to-digital converter circuit A/D1 through a subtractor circuit, similar operation can be carried out.

In each of the subtractor circuits D2 to D4, the negative terminal voltage of the storage device to which the subtractor circuit is connected is subtracted from the positive terminal voltage thereof so that the terminal-to-terminal voltage of the storage device is detected.

The detected terminal-to-terminal voltages of the storage devices B1 to B4 are supplied to the selector circuit SE through their corresponding analog-to-digital converter circuits A/D1 to A/D4 respectively. The detected voltage of a storage device selected by the selector circuit SE is outputted as serial data from the not-shown parallel-to-serial converter circuit P/S through an isolator PH (shown in the upper of FIG. 5) such as a photo-coupler.

In addition, in the selector circuit SE, a control command is given from the outside to a sub-controller SC through an isolator PH (shown in the lower of FIG. 5) such as a photo-coupler. By the output from the sub-controller SC, the selector circuit SE is controlled to output detected voltages of a plurality of storage devices to the outside.

It is effective that signals are inputted or outputted through an isolator such as a photo-coupler because the storage devices can be electrically isolated from external circuits.

In addition, it is desired that the region of the voltage detection circuit shown in FIG. 5 by the chain line, including the plurality of storage devices connected in series, is formed as one module.

In addition, the components of the voltage detection circuit in FIG. 5 including the subtractors, the analog-to-digital converter circuits and the selector circuit are supplied with operating voltage sources from the storage devices in the module respectively, as illustrated.

When the circuit of FIG. 5 is formed as one module, a pair of opposite terminals of the plurality of storage devices connected in series, a signal output terminal from the selector circuit and a signal input terminal for giving a command to the selector circuit from the outside are provided outside the module.

In addition, when the voltage detection circuit of FIG. 5 is formed into a module, it can be chosen whether the isolators PH constituted by photo-couplers or the like are provided inside the module or outside the module.

When a plurality of modules shown in FIG. 5 are connected in series or in parallel, a desired system adapted to the voltage and current for applications can be formed.

Further, although the number of storage devices to be connected in series is four in FIGS. 1 to 5, not to say, a desired number of storage devices may be connected.

Incidentally, although the plurality of storage devices B1 to B4 and the terminal-to-terminal voltage generator circuits are connected directly in the voltage detection circuit in each of FIGS. 4 and 5, semiconductor switching devices maybe inserted between the storage devices and their corresponding terminal-to-terminal voltage generator circuits respectively. In this case, the configuration as shown in FIGS. 1 and 2 may be adopted so that a plurality of semiconductor switching devices can be turned ON/OFF in accordance with a single external signal.

As described above, according to the invention, there is provided a current breaker circuit for storage devices by which currents flowing in loads are broken in accordance with a single external control signal, while the loads are connected between terminals of a plurality of storage devices connected in series, respectively. The current breaker circuit includes semiconductor switching devices inserted between the storage devices and the loads respectively, a unit for supplying the external control signal to at least one of the semiconductor switching devices, and a control signal generating unit for generating an ON/OFF signal in response to an electric change based on turning ON/OFF of the semiconductor switching device supplied with the external control signal, the ON/OFF signal being supplied to other semiconductor switching devices. Accordingly, there is an effect that currents supplied to the plurality of loads from the plurality of storage devices connected in series can be surely broken in accordance with a single external control signal without using any high-voltage withstanding switch or any expensive photo-coupler.

In addition, according to the invention, the external control signal is supplied to at least two adjacent ones of the semiconductor switching devices simultaneously. Accordingly, the current breaker circuit for storage devices can be formed out of a smaller number of constituent members.

In addition, according to the invention, the control signal generating unit supplies the ON/OFF signal to at least two adjacent ones of the semiconductor switching devices simultaneously. Accordingly, the number of control signal generator circuits can be reduced.

In addition, according to the invention, the semiconductor switching device supplied with the external control signal is formed as a semiconductor switching device connected to a lower voltage side among the storage devices connected in series. Accordingly, the potential with which the switch is connected can be made lower.

In addition, according to the invention, the ON/OFF signal is supplied to the semiconductor switching devices through diodes respectively. Accordingly, high voltage can be prevented from being applied to the control terminals of the semiconductor switching devices.

Particularly, when the ON/OFF signal is designed to be supplied simultaneously to at least two adjacent ones of the semiconductor switching devices connected in series, there is an effect that the semiconductor switching devices are prevented from being broken.

In addition, according to the invention, the loads are formed as a voltage detection circuit for detecting terminal-to-terminal voltages of the plurality of storage devices connected in series. Accordingly, even a very small current supplied to the voltage detection circuit can be broken surely.

Further, a voltage detection circuit for storage devices according to the invention is designed so that:

a plurality of terminal-to-terminal voltage generator circuits are provided;

each of the terminal-to-terminal voltage generator circuits is constituted by a storage device, a subtractor circuit and an A/D converter circuit, the subtractor circuit being supplied with a positive terminal voltage (Vn+1) and a negative terminal voltage (Vn) of the storage device and outputting a terminal-to-terminal voltage (Vno) of the storage device, the A/D converter circuit being supplied with the output of the subtractor circuit and outputting digital data;

the storage devices provided in the plurality of terminal-to-terminal voltage generator circuits are connected in series;

outputs of the A/D converter circuits provided respectively in the plurality of terminal-to-terminal voltage generator circuits are supplied to a selector circuit, which selects one piece of output data from the parallel output data supplied from the plurality of A/D converter circuits; and

the selected piece of output data is supplied to a parallel-to-serial converter circuit, which converts the supplied piece of output data into serial data, and outputs the converted serial data, so that a terminal-to-terminal voltage of any desired one of the plurality of storage devices connected in series is obtained as the serial data.

In the voltage detection circuit for storage devices configured thus, the terminal-to-terminal voltages of the plurality of storage devices connected in series can be detected accurately and selectively respectively to be outputted.

In addition, according to the invention, an external select control signal is supplied to the selector circuit. Accordingly, the terminal-to-terminal voltage of a desired one of the storage devices can be outputted in accordance with an external instruction.

In addition, according to the invention, a plurality of parallel-to-serial converter circuits may be provided at a pre-stage of the selector circuit so that the selector circuit can select one from the outputs converted into serial data by the parallel-to-serial converter circuits.

In addition, according to the invention, the serial data and/or the select control signal are supplied through an isolator. Accordingly, the serial data and/or the select control signal can be electrically isolated from external circuits.

Further, a voltage detection circuit for storage devices according to the invention is formed so that:

at least a plurality of terminal-to-terminal voltage generator circuits are provided;

each of the terminal-to-terminal voltage generator circuits is constituted by a storage device, a subtractor circuit and an A/D converter circuit, the subtractor circuit being supplied with a positive terminal voltage (Vn+1) and a negative terminal voltage (Vn) of the storage device and outputting a terminal-to-terminal voltage (Vno) of the storage device, the A/D converter circuit being supplied with the output of the subtractor circuit and outputting digital data;

the storage devices provided in the plurality of terminal-to-terminal voltage generator circuits are connected in series;

a selector circuit selects one piece of output data from output data of the A/D converter circuits respectively provided in the plurality of terminal-to-terminal voltage generator circuits;

the selected piece of output data is supplied to a parallel-to-serial converter circuit, which converts the supplied piece of output data into serial data;

the terminal-to-terminal voltage generator circuits, the selector circuit and the parallel-to-serial converter circuit are included in a single module; and

a pair of opposite terminals of the plurality of storage devices connected in series, and an output terminal of the serial data are led out as external terminals of the module.

Since the unit module is formed thus, a desired system can be constructed easily by use of a plurality of such modules.

In addition, according to the invention, a select control signal from the outside of the module is supplied as a serial signal to the selector circuit. Accordingly, signals can be transmitted/received between the module and the outside through a small number of signal lines.

In addition, according to the invention, a plurality of parallel-to-serial converter circuits may be provided at a pre-stage of the selector circuit so that the selector circuit can select one from the outputs converted into serial data by the parallel-to-serial converter circuits.

In addition, according to the invention, an isolator for electrically isolating the serial data and/or the select control signal may be provided in the module.

Further, according to the invention, an abnormality detection circuit for detecting abnormality of a current breaker circuit breaking currents in accordance with a single external control signal is provided. The currents flow into a plurality of loads which are respectively connected between terminals of a plurality of storage devices connected in series. In the abnormality detection circuit, operation abnormality of the current breaker circuit is detected on the basis of the single external control signal and a terminal-to-terminal voltage of a final-stage one of the loads, so that abnormality of the operation of the current breaker circuit as a whole can be detected easily.

In addition, according to the invention, a first photo-coupler and a second photo-coupler may be provided and connected to opposite terminals of the final-stage load respectively. In this case, the external control signal is supplied to the second photo-coupler only for an abnormality detection period so as to turn on the abnormality detection circuit and thereby obtain a detection result through the first photo-coupler. Thus, a current is allowed to flow into a light emitting device of the first photo-coupler and a light receiving device of the second photo-coupler only for the detection period. Accordingly, it is not necessary to make a constant conduction. It is therefore possible to prevent useless consumption of electric power. 

What is claimed is:
 1. A current breaker circuit for turning off currents flowing in loads in accordance with a single external control signal, said loads being connected respectively between terminals of a plurality of storage devices connected in series, said current breaker circuit comprising: semiconductor switching devices provided between said storage devices and said loads respectively; a unit for supplying the external control signal to at least one of said semiconductor switching devices; and a control signal generating unit for generating an ON/OFF signal in response to an electric change based on turning ON/OFF of said semiconductor switching device supplied with the external control signal, so as to supply the ON/OFF signal to other semiconductor switching devices in turn.
 2. The current breaker circuit for storage devices according to claim 1, wherein the external control signal is supplied to at least two adjacent ones of said semiconductor switching devices simultaneously.
 3. The current breaker circuit for storage devices according to claim 1, wherein said control signal generating unit supplies the ON/OFF signal to at least two adjacent ones of said semiconductor switching devices.
 4. The current breaker circuit for storage devices according to claim 1, wherein said semiconductor switching device supplied with the external control signal is a semiconductor switching device connected to a lower voltage side among said storage devices connected in series.
 5. The current breaker circuit for storage devices according to claim 1, wherein the ON/OFF signal is supplied to said semiconductor switching devices through diodes respectively.
 6. The current breaker circuit for storage devices according to claim 1, wherein said loads are formed as a voltage detection circuit for detecting terminal-to-terminal voltages of said plurality of storage devices connected in series.
 7. An abnormality detection circuit for detecting abnormality of a current breaker circuit, wherein said current breaker circuit breaks currents flowing into a plurality of loads which are respectively connected between terminals of a plurality of storage devices connected in series, and the abnormality of said current breaker circuit is detected on the basis of the single external control signal and a terminal-to-terminal voltage of a final-stage load among said plurality of loads.
 8. The abnormality detection circuit according to claim 7, further comprising: a first photo-coupler and a second photo-coupler provided and connected to opposite terminals of said final-stage load respectively, wherein the external control signal is supplied to said second photo-coupler only for an abnormality detection period so as to turn on said abnormality detection circuit and obtain a detection result through said first photo-coupler. 